This invention relates to an industrial robot and, more particularly, to an industrial robot equipped with a special hand driving mechanism.
Industrial robots usually have a gripping device mounted at the end of a hand which extends from the robot body. The body also accommodates control and drive devices. The gripping device is adapted to grasp a workpiece placed on a pallet and to carry the workpiece over a predetermined path to another location or to the chuck of a machine tool. In response to the demand for reduction in size, compact industrial robots have recently been developed which can be installed on a machine tool per se.
In general, an industrial robot is capable of picking up an unfinished workpiece from a work feeder and loading it into the chuck of a lathe or the like, or of unloading a machined workpiece from the chuck and placing it on a table. Since the surface of the unfinished workpiece to be held by the chuck lies perpendicular to the surface of the feeder or of the table, the gripping member (hand) must be capable of being rotated through an angle of 90 degrees at the wrist connected thereto in order for the workpiece to be oriented correctly when travelling between the chuck and feeder or table.
In robots provided with a double-hand arrangement, i.e., two grippers are provided and disposed one above the other, it is required that one gripper unload a machined workpiece from the chuck and then rotate 180 degrees to permit the other gripper, which is holding an unfinished workpiece, to load that unfinished workpiece into the chuck. A further requirement is that one gripper holding a machined workpiece place the workpiece on the table and then rotate through an angle of 180 degrees to permit the other gripper to pick up an unfinished workpiece from the workpiece feeder. Thus the hand grippers must be positionable through the wrist mechanism at four points 0.degree., .+-.90.degree., and 180.degree.. Heretofore, however, a small-size, structurally simple industrial robot capable of four-point positioning of the hand has not been available.